The present invention relates in general to mechanical linkages and in particular to a rudder linkage with thermal compensation features utilized in an airplane fin to control the airplane's rudder.
During climb, the fin structure of a modern jet airplane cools more rapidly than the rudder control linkages inside the fin resulting in a rudder drift to the left or right depending upon the design of the linkages and the location of the linkage pivot points on the fin structure. To compensate, it has been necessary for the pilot to make frequent corrections during flight to lateral and directional trim. During cruise the fin structure and the control linkage inside eventually reaches the same temperature and corrections, opposite in direction to those applied during climb, are again necessary to maintain proper trim. Upon descent the fin structure warms up faster than the aforementioned linkages and rods, resulting in a rudder drift in an opposite direction.
These rudder drifts together with resultant directional changes and required corrections are undesirable and are amplified in very sensitive control systems having large yaw authority. Furthermore, fin bending caused by winds or otherwise adds a yaw input in an undesirable direction as the fin is subjected to sideload.